Asunder especially is pretty handily the best video game tie-in I've read.
Both "Asunder" and "The Masked Empire" stand out as the only video-game tie-ins I know which are on the same level as reasonably good regular written fiction. I'm very happy to see that happening since it may indicate that video games as a storytelling medium are in the process of acquiring some maturity. It is very odd, however, to see these good examples coming from the same developer as the worst one (ME:Deception). Man, that was the epitome of awful, and I've seen a lot of awful over the years.
Anyway, I don't think "Asunder" and "The Masked Empire" are required reading, but they do enrich the world and let you view things from a different perspective, and since they're actually fun to read, there is no reason not to do that.